Mitral Valve Prolapse

September 17, 2011

Mitral valve prolapse (MVP) is the most common congenital valvular heart disease in adults and has become the most frequent valvular cause of chronic mitral regurgitation (leakiness) in the United States.

The prevalence of this disease in our country varies according to the sources in the literature due to a lack of strict criteria for diagnosis and differences in study design. This condition has been reported to occur in 5-10% of the general population, with the prevalence being highest in young women. However, this finding was based on studies using old diagnostic criteria for this condition. Dr. Levine and colleagues at the Massachusetts General Hospital showed that the supposed epidemic of Mitral valve prolapse was created by misinterpretation of echocardiographic findings. The Framingham Study examined 1,845 women and 1,646 men using the current two-dimensional echocardiographic criteria for the diagnosis of Mitral valve prolapse. The findings were: disease prevalence of 2.4%, no gender difference and no age group predominance.

The mitral valve is a bileaflet structure that separates the left atrium and the left ventricle (the upper and lower left-sided chambers of the heart). It is composed of the anterior and posterior leaflets, the chordae tendineae that are attached to the papillary muscles, and the mitral valve annulus. In Mitral valve prolapse disease, there is thickening and redundancy of the leaflets, elongation, thinning and occasional rupture of the chordae tendineae, and dilatation of the annulus. Histologically, there is substitution of the normal fibrous tissue of the valve structure by a myxomatous process that is responsible for the above changes. Both leaflets can be involved, but the posterior leaflet is the most commonly affected one.

Mitral valve prolapse, floppy mitral valve, click/murmur syndrome, Barlow’s syndrome, and myxomatous mitral valve disease are all different names for this disease. The name prolapse comes from the fact that one or both leaflets are displaced above the mitral valve ring into the left atrium during systole, the contraction phase of the heart. Mitral valve prolapse can be inherited as an autosomal dominant condition with incomplete penetrance or, less commonly, as an X-chromosome-linked disorder in which males are affected and females are carriers. It can be associated with connective tissue disorders such as Marfan syndrome, Ehlers-Danlos syndrome, adult polycystic kidney disease, anterior chest deformity, scoliosis, and kyphosis. It can be associated with tricuspid valve prolapse as well.

The diagnosis of Mitral valve prolapse is based on physical examination of the heart with confirmatory echocardiographic findings. On auscultation of the heart, the typical finding is the midsystolic click, which may or may not be associated with a late systolic murmur of mitral regurgitation because of lack of complete coaptation of the anterior and posterior leaflets. Echocardiography is the most useful tool that can show in real time the prolapsing mitral leaflets, the thickened leaflets, redundant chordae tendineae, and dilated annulus. It can also reveal the severity of mitral regurgitation, if there is any, as well as determine whether there is dilatation of the heart chambers and deterioration of heart function.

Mitral regurgitation is one of the most common complications of Mitral valve prolapse disease. Fortunately, the majority of patients have only mild regurgitation or none at all. However, 2-7% of patients progress to severe regurgitation, requiring surgical treatment. Furthermore, the presence of severe regurgitation is a risk factor for heart failure, sudden death, arrhythmias, and congestive heart failure. Symptoms suggestive of hemodynamically significant mitral regurgitation are shortness of breath, decreased exercise tolerance with easy fatigability, and dizziness. Once the patient develops the above symptoms, it is usually indicative that left ventricular contractility is beginning to decrease and surgical treatment with either valve repair or replacement is indicated. Chordae rupture can complicate Mitral valve prolapse and can occur spontaneously or during exercise. Mitral valve repair is the treatment of choice over valve replacement when the anatomy is favorable. This is because the former is related to a better outcome with regard to preservation of ventricular function. Isolated posterior leaflet prolapse has better operative success results with lower reoperation rate than anterior or bileaflet prolapse. Indications for surgery in Mitral valve prolapse are: (a) development of symptoms of heart failure; (b) asymptomatic patients with severe regurgitation and evidence of left ventricular systolic dysfunction or left ventricular dilatation;

Infective endocarditis (infection involving the mitral valve caused by bacteria or fungus) is a possible complication of Mitral valve prolapse, mainly when it is associated with mitral regurgitation and significant leaflet thickening. Therefore, patients with these two conditions should be advised to take antibiotics prior to any invasive procedures such as dental cleaning and endoscopy with biopsy.

Based on observational studies, the risk of strokes and transient ischemic cerebral attacks in Mitral valve prolapse is very low: estimated to be 1 in 11,000 per year. Many people with Mitral valve prolapse present with a constellation of nonspecific symptoms that cannot be attributed to advanced valve dysfunction, such as panic attacks, anxiety, atypical chest pain, and palpitations without arrhythmias. This constellation of symptoms has been called Mitral valve prolapse syndrome. Many physicians believe that these symptoms are coincidental and that the link between them and the disease is accidental because of the inaccuracy of original studies suggesting an association. It is possible, however, that the autonomic nervous system and neuroendocrine dysfunction found in some patients with Mitral valve prolapse may be responsible for some of these symptoms. Further investigation is warranted to confirm this possibility. Patients with these symptoms benefit from reassurance about the benign nature of this disorder, changes in lifestyle, including aerobic exercise, avoidance of stimulants such as caffeine and alcohol, and reduction of stress.

Asymptomatic patients with Mitral valve prolapse may engage in exercise and competitive activities. However, patients with mitral regurgitation should avoid weight lifting. Patients with Mitral valve prolapse should be followed with a physical examination every 2-3 years. A new murmur or development of symptoms should prompt further evaluation with an echocardiogram.